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 * ***** END LICENSE BLOCK ***** */

/**************************************************************************************
 * Fixed-point MP3 decoder
 * Jon Recker (jrecker@real.com), Ken Cooke (kenc@real.com)
 * July 2003
 *
 * huffman.c - Huffman decoding of transform coefficients
 **************************************************************************************/

#include "coder.h"

/* helper macros - see comments in hufftabs.c about the format of the huffman tables */
#define GetMaxbits(x)   ((int)( (((unsigned short)(x)) >>  0) & 0x000f))
#define GetHLen(x)      ((int)( (((unsigned short)(x)) >> 12) & 0x000f))
#define GetCWY(x)       ((int)( (((unsigned short)(x)) >>  8) & 0x000f))
#define GetCWX(x)       ((int)( (((unsigned short)(x)) >>  4) & 0x000f))
#define GetSignBits(x)  ((int)( (((unsigned short)(x)) >>  0) & 0x000f))

#define GetHLenQ(x)     ((int)( (((unsigned char)(x)) >> 4) & 0x0f))
#define GetCWVQ(x)      ((int)( (((unsigned char)(x)) >> 3) & 0x01))
#define GetCWWQ(x)      ((int)( (((unsigned char)(x)) >> 2) & 0x01))
#define GetCWXQ(x)      ((int)( (((unsigned char)(x)) >> 1) & 0x01))
#define GetCWYQ(x)      ((int)( (((unsigned char)(x)) >> 0) & 0x01))

/* apply sign of s to the positive number x (save in MSB, will do two's complement in dequant) */
#define ApplySign(x, s) { (x) |= ((s) & 0x80000000); }

/**************************************************************************************
 * Function:    DecodeHuffmanPairs
 *
 * Description: decode 2-way vector Huffman codes in the "bigValues" region of spectrum
 *
 * Inputs:      valid BitStreamInfo struct, pointing to start of pair-wise codes
 *              pointer to xy buffer to received decoded values
 *              number of codewords to decode
 *              index of Huffman table to use
 *              number of bits remaining in bitstream
 *
 * Outputs:     pairs of decoded coefficients in vwxy
 *              updated BitStreamInfo struct
 *
 * Return:      number of bits used, or -1 if out of bits
 *
 * Notes:       assumes that nVals is an even number
 *              si_huff.bit tests every Huffman codeword in every table (though not
 *                necessarily all linBits outputs for x,y > 15)
 **************************************************************************************/
static int DecodeHuffmanPairs(int* xy, int nVals, int tabIdx, int bitsLeft, unsigned char* buf, int bitOffset)
{
    int i, x, y;
    int cachedBits, padBits, len, startBits, linBits, maxBits, minBits;
    HuffTabType tabType;
    unsigned short cw, *tBase, *tCurr;
    unsigned int cache;

    if(nVals <= 0)
        return 0;

    if (bitsLeft < 0)
        return -1;
    startBits = bitsLeft;

    tBase = (unsigned short*)(huffTable + huffTabOffset[tabIdx]);
    linBits = huffTabLookup[tabIdx].linBits;
    tabType = huffTabLookup[tabIdx].tabType;

    ASSERT(!(nVals & 0x01));
    ASSERT(tabIdx < HUFF_PAIRTABS);
    ASSERT(tabIdx >= 0);
    ASSERT(tabType != invalidTab);

    /* initially fill cache with any partial byte */
    cache = 0;
    cachedBits = (8 - bitOffset) & 0x07;
    if (cachedBits)
        cache = (unsigned int)(*buf++) << (32 - cachedBits);
    bitsLeft -= cachedBits;

    if (tabType == noBits) {
        /* table 0, no data, x = y = 0 */
        for (i = 0; i < nVals; i += 2) {
            xy[i + 0] = 0;
            xy[i + 1] = 0;
        }
        return 0;
    }
    else if (tabType == oneShot) {
        /* single lookup, no escapes */
        maxBits = GetMaxbits(tBase[0]);
        tBase++;
        padBits = 0;
        while (nVals > 0) {
            /* refill cache - assumes cachedBits <= 16 */
            if (bitsLeft >= 16) {
                /* load 2 new bytes into left-justified cache */
                cache |= (unsigned int)(*buf++) << (24 - cachedBits);
                cache |= (unsigned int)(*buf++) << (16 - cachedBits);
                cachedBits += 16;
                bitsLeft -= 16;
            }
            else {
                /* last time through, pad cache with zeros and drain cache */
                if (cachedBits + bitsLeft <= 0) return -1;
                if (bitsLeft > 0)   cache |= (unsigned int)(*buf++) << (24 - cachedBits);
                if (bitsLeft > 8)   cache |= (unsigned int)(*buf++) << (16 - cachedBits);
                cachedBits += bitsLeft;
                bitsLeft = 0;

                cache &= (signed int)0x80000000 >> (cachedBits - 1);
                padBits = 11;
                cachedBits += padBits;  /* okay if this is > 32 (0's automatically shifted in from right) */
            }

            /* largest maxBits = 9, plus 2 for sign bits, so make sure cache has at least 11 bits */
            while (nVals > 0 && cachedBits >= 11 ) {
                cw = tBase[cache >> (32 - maxBits)];
                len = GetHLen(cw);
                cachedBits -= len;
                cache <<= len;

                x = GetCWX(cw);
                if (x)  {
                    ApplySign(x, cache);
                    cache <<= 1;
                    cachedBits--;
                }
                y = GetCWY(cw);
                if (y)  {
                    ApplySign(y, cache);
                    cache <<= 1;
                    cachedBits--;
                }

                /* ran out of bits - should never have consumed padBits */
                if (cachedBits < padBits)
                    return -1;

                *xy++ = x;
                *xy++ = y;
                nVals -= 2;
            }
        }
        bitsLeft += (cachedBits - padBits);
        return (startBits - bitsLeft);
    }
    else if (tabType == loopLinbits || tabType == loopNoLinbits) {
        tCurr = tBase;
        padBits = 0;
        while (nVals > 0) {
            /* refill cache - assumes cachedBits <= 16 */
            if (bitsLeft >= 16) {
                /* load 2 new bytes into left-justified cache */
                cache |= (unsigned int)(*buf++) << (24 - cachedBits);
                cache |= (unsigned int)(*buf++) << (16 - cachedBits);
                cachedBits += 16;
                bitsLeft -= 16;
            }
            else {
                /* last time through, pad cache with zeros and drain cache */
                if (cachedBits + bitsLeft <= 0) return -1;
                if (bitsLeft > 0)   cache |= (unsigned int)(*buf++) << (24 - cachedBits);
                if (bitsLeft > 8)   cache |= (unsigned int)(*buf++) << (16 - cachedBits);
                cachedBits += bitsLeft;
                bitsLeft = 0;

                cache &= (signed int)0x80000000 >> (cachedBits - 1);
                padBits = 11;
                cachedBits += padBits;  /* okay if this is > 32 (0's automatically shifted in from right) */
            }

            /* largest maxBits = 9, plus 2 for sign bits, so make sure cache has at least 11 bits */
            while (nVals > 0 && cachedBits >= 11 ) {
                maxBits = GetMaxbits(tCurr[0]);
                cw = tCurr[(cache >> (32 - maxBits)) + 1];
                len = GetHLen(cw);
                if (!len) {
                    cachedBits -= maxBits;
                    cache <<= maxBits;
                    tCurr += cw;
                    continue;
                }
                cachedBits -= len;
                cache <<= len;

                x = GetCWX(cw);
                y = GetCWY(cw);

                if (x == 15 && tabType == loopLinbits) {
                    minBits = linBits + 1 + (y ? 1 : 0);
                    if (cachedBits + bitsLeft < minBits)
                        return -1;
                    while (cachedBits < minBits) {
                        cache |= (unsigned int)(*buf++) << (24 - cachedBits);
                        cachedBits += 8;
                        bitsLeft -= 8;
                    }
                    if (bitsLeft < 0) {
                        cachedBits += bitsLeft;
                        bitsLeft = 0;
                        cache &= (signed int)0x80000000 >> (cachedBits - 1);
                    }
                    x += (int)(cache >> (32 - linBits));
                    cachedBits -= linBits;
                    cache <<= linBits;
                }
                if (x)  {
                    ApplySign(x, cache);
                    cache <<= 1;
                    cachedBits--;
                }

                if (y == 15 && tabType == loopLinbits) {
                    minBits = linBits + 1;
                    if (cachedBits + bitsLeft < minBits)
                        return -1;
                    while (cachedBits < minBits) {
                        cache |= (unsigned int)(*buf++) << (24 - cachedBits);
                        cachedBits += 8;
                        bitsLeft -= 8;
                    }
                    if (bitsLeft < 0) {
                        cachedBits += bitsLeft;
                        bitsLeft = 0;
                        cache &= (signed int)0x80000000 >> (cachedBits - 1);
                    }
                    y += (int)(cache >> (32 - linBits));
                    cachedBits -= linBits;
                    cache <<= linBits;
                }
                if (y)  {
                    ApplySign(y, cache);
                    cache <<= 1;
                    cachedBits--;
                }

                /* ran out of bits - should never have consumed padBits */
                if (cachedBits < padBits)
                    return -1;

                *xy++ = x;
                *xy++ = y;
                nVals -= 2;
                tCurr = tBase;
            }
        }
        bitsLeft += (cachedBits - padBits);
        return (startBits - bitsLeft);
    }

    /* error in bitstream - trying to access unused Huffman table */
    return -1;
}

/**************************************************************************************
 * Function:    DecodeHuffmanQuads
 *
 * Description: decode 4-way vector Huffman codes in the "count1" region of spectrum
 *
 * Inputs:      valid BitStreamInfo struct, pointing to start of quadword codes
 *              pointer to vwxy buffer to received decoded values
 *              maximum number of codewords to decode
 *              index of quadword table (0 = table A, 1 = table B)
 *              number of bits remaining in bitstream
 *
 * Outputs:     quadruples of decoded coefficients in vwxy
 *              updated BitStreamInfo struct
 *
 * Return:      index of the first "zero_part" value (index of the first sample
 *                of the quad word after which all samples are 0)
 *
 * Notes:        si_huff.bit tests every vwxy output in both quad tables
 **************************************************************************************/
static int DecodeHuffmanQuads(int* vwxy, int nVals, int tabIdx, int bitsLeft, unsigned char* buf, int bitOffset)
{
    int i, v, w, x, y;
    int len, maxBits, cachedBits, padBits;
    unsigned int cache;
    unsigned char cw, *tBase;

    if (bitsLeft <= 0)
        return 0;

    tBase = (unsigned char*)quadTable + quadTabOffset[tabIdx];
    maxBits = quadTabMaxBits[tabIdx];

    /* initially fill cache with any partial byte */
    cache = 0;
    cachedBits = (8 - bitOffset) & 0x07;
    if (cachedBits)
        cache = (unsigned int)(*buf++) << (32 - cachedBits);
    bitsLeft -= cachedBits;

    i = padBits = 0;
    while (i < (nVals - 3)) {
        /* refill cache - assumes cachedBits <= 16 */
        if (bitsLeft >= 16) {
            /* load 2 new bytes into left-justified cache */
            cache |= (unsigned int)(*buf++) << (24 - cachedBits);
            cache |= (unsigned int)(*buf++) << (16 - cachedBits);
            cachedBits += 16;
            bitsLeft -= 16;
        }
        else {
            /* last time through, pad cache with zeros and drain cache */
            if (cachedBits + bitsLeft <= 0) return i;
            if (bitsLeft > 0)   cache |= (unsigned int)(*buf++) << (24 - cachedBits);
            if (bitsLeft > 8)   cache |= (unsigned int)(*buf++) << (16 - cachedBits);
            cachedBits += bitsLeft;
            bitsLeft = 0;

            cache &= (signed int)0x80000000 >> (cachedBits - 1);
            padBits = 10;
            cachedBits += padBits;  /* okay if this is > 32 (0's automatically shifted in from right) */
        }

        /* largest maxBits = 6, plus 4 for sign bits, so make sure cache has at least 10 bits */
        while (i < (nVals - 3) && cachedBits >= 10 ) {
            cw = tBase[cache >> (32 - maxBits)];
            len = GetHLenQ(cw);
            cachedBits -= len;
            cache <<= len;

            v = GetCWVQ(cw);
            if(v) {
                ApplySign(v, cache);
                cache <<= 1;
                cachedBits--;
            }
            w = GetCWWQ(cw);
            if(w) {
                ApplySign(w, cache);
                cache <<= 1;
                cachedBits--;
            }
            x = GetCWXQ(cw);
            if(x) {
                ApplySign(x, cache);
                cache <<= 1;
                cachedBits--;
            }
            y = GetCWYQ(cw);
            if(y) {
                ApplySign(y, cache);
                cache <<= 1;
                cachedBits--;
            }

            /* ran out of bits - okay (means we're done) */
            if (cachedBits < padBits)
                return i;

            *vwxy++ = v;
            *vwxy++ = w;
            *vwxy++ = x;
            *vwxy++ = y;
            i += 4;
        }
    }

    /* decoded max number of quad values */
    return i;
}

/**************************************************************************************
 * Function:    DecodeHuffman
 *
 * Description: decode one granule, one channel worth of Huffman codes
 *
 * Inputs:      MP3DecInfo structure filled by UnpackFrameHeader(), UnpackSideInfo(),
 *                and UnpackScaleFactors() (for this granule)
 *              buffer pointing to start of Huffman data in MP3 frame
 *              pointer to bit offset (0-7) indicating starting bit in buf[0]
 *              number of bits in the Huffman data section of the frame
 *                (could include padding bits)
 *              index of current granule and channel
 *
 * Outputs:     decoded coefficients in hi->huffDecBuf[ch] (hi pointer in mp3DecInfo)
 *              updated bitOffset
 *
 * Return:      length (in bytes) of Huffman codes
 *              bitOffset also returned in parameter (0 = MSB, 7 = LSB of
 *                byte located at buf + offset)
 *              -1 if null input pointers, huffBlockBits < 0, or decoder runs
 *                out of bits prematurely (invalid bitstream)
 **************************************************************************************/
int DecodeHuffman(MP3DecInfo* mp3DecInfo, unsigned char* buf, int* bitOffset, int huffBlockBits, int gr, int ch)
{
    int r1Start, r2Start, rEnd[4];  /* region boundaries */
    int i, w, bitsUsed, bitsLeft;
    unsigned char* startBuf = buf;

    FrameHeader* fh;
    SideInfo* si;
    SideInfoSub* sis;
    //ScaleFactorInfo *sfi;
    HuffmanInfo* hi;

    /* validate pointers */
    if (!mp3DecInfo || !mp3DecInfo->FrameHeaderPS || !mp3DecInfo->SideInfoPS || !mp3DecInfo->ScaleFactorInfoPS || !mp3DecInfo->HuffmanInfoPS)
        return -1;

    fh = ((FrameHeader*)(mp3DecInfo->FrameHeaderPS));
    si = ((SideInfo*)(mp3DecInfo->SideInfoPS));
    sis = &si->sis[gr][ch];
    //sfi = ((ScaleFactorInfo *)(mp3DecInfo->ScaleFactorInfoPS));
    hi = (HuffmanInfo*)(mp3DecInfo->HuffmanInfoPS);

    if (huffBlockBits < 0)
        return -1;

    /* figure out region boundaries (the first 2*bigVals coefficients divided into 3 regions) */
    if (sis->winSwitchFlag && sis->blockType == 2) {
        if (sis->mixedBlock == 0) {
            r1Start = fh->sfBand->s[(sis->region0Count + 1) / 3] * 3;
        }
        else {
            if (fh->ver == MPEG1) {
                r1Start = fh->sfBand->l[sis->region0Count + 1];
            }
            else {
                /* see MPEG2 spec for explanation */
                w = fh->sfBand->s[4] - fh->sfBand->s[3];
                r1Start = fh->sfBand->l[6] + 2 * w;
            }
        }
        r2Start = MAX_NSAMP;    /* short blocks don't have region 2 */
    }
    else {
        r1Start = fh->sfBand->l[sis->region0Count + 1];
        r2Start = fh->sfBand->l[sis->region0Count + 1 + sis->region1Count + 1];
    }

    /* offset rEnd index by 1 so first region = rEnd[1] - rEnd[0], etc. */
    rEnd[3] = MIN(MAX_NSAMP, 2 * sis->nBigvals);
    rEnd[2] = MIN(r2Start, rEnd[3]);
    rEnd[1] = MIN(r1Start, rEnd[3]);
    rEnd[0] = 0;

    /* rounds up to first all-zero pair (we don't check last pair for (x,y) == (non-zero, zero)) */
    hi->nonZeroBound[ch] = rEnd[3];

    /* decode Huffman pairs (rEnd[i] are always even numbers) */
    bitsLeft = huffBlockBits;
    for (i = 0; i < 3; i++) {
        bitsUsed = DecodeHuffmanPairs(hi->huffDecBuf[ch] + rEnd[i], rEnd[i + 1] - rEnd[i], sis->tableSelect[i], bitsLeft, buf, *bitOffset);
        if (bitsUsed < 0 || bitsUsed > bitsLeft)    /* error - overran end of bitstream */
            return -1;

        /* update bitstream position */
        buf += (bitsUsed + *bitOffset) >> 3;
        *bitOffset = (bitsUsed + *bitOffset) & 0x07;
        bitsLeft -= bitsUsed;
    }

    /* decode Huffman quads (if any) */
    hi->nonZeroBound[ch] += DecodeHuffmanQuads(hi->huffDecBuf[ch] + rEnd[3], MAX_NSAMP - rEnd[3], sis->count1TableSelect, bitsLeft, buf, *bitOffset);

    ASSERT(hi->nonZeroBound[ch] <= MAX_NSAMP);
    for (i = hi->nonZeroBound[ch]; i < MAX_NSAMP; i++)
        hi->huffDecBuf[ch][i] = 0;

    /* If bits used for 576 samples < huffBlockBits, then the extras are considered
     *  to be stuffing bits (throw away, but need to return correct bitstream position)
     */
    buf += (bitsLeft + *bitOffset) >> 3;
    *bitOffset = (bitsLeft + *bitOffset) & 0x07;

    return (buf - startBuf);
}

